There are extant a wide variety of drive mechanisms for converting rotary to linear movement in a power transmission circuit. Of particular interest to those skilled in the art when considering the present invention is the Hall et al. U.S. Pat. No. 3,044,312. Also of interest in this regard are the Bratschi U.S. Pat. No. 3,372,599; the Nagel et al. U.S. Pat. No. 3,273,408; and the Morris U.S. Pat. No. 2,598,709. The complexity and, consequently, the cost of these drive mechanisms have minimized their value and restricted their use, however.